Dunn said witnesses' descriptions of the vehicle led police to Avila, who was driving a silver Mitsubishi and carrying a handgun. Police dogs helped capture Avila when authorities conducted the car stop, Dunn added. Witnesses gave police a partial license plate number of the vehicle, Dunn said.

Officers first responded shortly after 8 p.m. to reports of a vehicle striking a pedestrian near Neighbors and Onondaga avenues, Dunn said.

While authorities were responding to the area, police received additional reports of shots fired in the 1800 block of Neighbors Avenue, Dunn added.

Ruiz said she did not hear the gunshots. Mariachis were performing during the celebration of the Virgin of Guadalupe, she said, and many children were at the gathering.

Witnesses told police that the vehicle that hit Karla had been involved in a drive-by shooting before speeding through an alley and out of the apartment complex. The girl apparently was struck in the alley as the car drove away.

Authorities have not located anyone who was struck by the gunfire.

"We are investigating it as possibly being gang-related," Dunn said of the shooting.